Machine tools used today such as routers, milling machines, drill presses, etc. generate a great deal of waste in the form of dust and large quantities of work chips and other materials when they cut into a workpiece. Disposal of the waste including sawdust, chips, and the like can be very difficult to carry out. The waste is a nuisance both on a work shop floor and, particularly, when the machine tool is being used in an area other than a workshop where the production of dust is even less desirable.
Wide broadcasting of the waste material produced by machine tools can, for some workpieces, be detrimental to the health of the operator of the machine as well as other workers in the immediate vicinity. Such waste products can also be dangerous since they tend to build up on the floor around the machine station, often causing the surface of the floor to become slippery and uncomfortable. Also, in the case of wood and other combustible workpieces, for example, a fire hazard may be created by waste such as sawdust.
Waste products generated during machine tooling operations can also be detrimental from an economic standpoint in that they often make it very difficult for the machine tool operator to view the workpiece since they often obstruct the operator's view of marked cutting lines, etc. The waste product can also get into the machinery itself and cause overheating and damage to the bearings, couplings, etc.
In the past, such machine tool operations have required either constant or frequent clean-up operations. In such cases, machinery is provided which positively removes the waste products from the immediate vicinity of the cutting or working tool. In most instances, such removal is accomplished by compressed air which is directed across the surface of the worktable to blow the waste produced toward a waste receptacle area from which it can be removed more conveniently.
The current trend in industry is to improve the environment of the worker to insure that health hazards are minimized. In woodworking facilities this trend has been accomplished by collecting wood particles and dust utilizing a vacuum means located in the vicinity of the origin of the wood particles and dust, and disposing of such waste in a collection bin. For example, U.S. Pat. No. 4,201,256 to Truhan discloses a modified safety cover for a saw blade that functions as a vacuum collector in cooperation with a collector bin located beneath the sawtable, whereby sawdust generated on the top of the workpiece as well as the bottom of the workpiece will be drawn directly into a vacuum transport conduit. The vacuum transport conduit transfers the sawdust and woodchip particles to the collection bin.
Some power tools such as routers, sanders, grinders and other woodcutting tools have been provided with vacuuming devices which, in most cases, are directly attached to the tool in such a way that a large portion of the waste products of the workpiece are transferred to the vacuum system and thus removed. For example, U.S. Pat. No. 4,742,855 to Hartley discloses a router which is surrounded by a dust collector collar which is vertically positionable relative to the workpiece by means of a pneumatic system. In operation, a vacuum force is applied to the top portion of the dust collector collar and is used to draw air upwardly from the workpiece past the router motor to a factory dust extraction means. Hartley has found that the upward flow of air enables the use of a fanless electric motor for the router inasmuch as the upward flow of air aids in cooling the electric motor of the router.
U.S. Pat. No. 4,750,536 to Grisley discloses a waste attachment for a router which includes a housing assembly having a portion thereof which is slidably positionable to be in contact with the workpiece being routed. The housing assembly is connected to a vacuum source which withdraws and collects debris from the workpiece.
While the above prior art waste collecting means have contributed significantly to the problem of how to remove and contain waste produced by machine tools, they are nevertheless inefficient in a number of ways. They may, for example, obstruct the operator's view and make it difficult for him to operate the tool along marked cutting lines. Also, in such prior art devices the vacuum force is often applied along a plane which is substantially parallel to and intersects the plane of the tool bit. This causes the vacuum force to work in a more random fashion than is desired, resulting in at least some of the waste either entering into a continuous movement about the tool without withdrawal from the area. Therefore, expulsion is produced from around the tool and the vacuum device without delivery to the vacuum removal system. Alternatively, turbulent motion around the tool for a longer period of time than is desired is produced with a resultant poor visibility of the relationship between the tool and the workpiece.
U.S. Pat. No. 3,837,383 to Ko discloses a vacuum assembly for a router which is made from a transparent material so that the operator can easily view the operation of the router. Additionally, Ko positions this vacuum suction means to be along a tangent relative to the normal helical arc of the waste materials as they travel from the cutting tool. In this regard, Ko has attempted to take advantage of the projectile or centrifugal force of the waste in order to augment the vacuum force and capture the waste.
In a quite different approach than that taken by Ko, U.S. Pat. No. 4,011,792 to Davis discloses a rotary tool exhaust that utilizes auxiliary jet tubes to inflict changes of direction of chips or particles thrown off as they leave the rotor tool, causing them to become readily airborne in an exhaust system passing through the hood. In principle, Davis utilizes the jet tubes to cause the chips or other particles to be dispersed upwardly so that they can become airborne and more easily subjected to removal by the exhaust system provided.
Generally, the control technology used on computer control routers consist of a local exhaust hood and a round brush installed at the router head. Despite this control, and the above-discussed developments in the art, significant quantities of wooddust are admitted into the workroom, notably when a large diameter router bit is used and the wood is routed under its surface.
In such routing operations the wooddust is emitted at a very high velocity because of the high surface velocity of the rotating router bit. This velocity may reach speeds of up to 15,000 feet per minute depending on the router bit diameter. To control this dust, the exhaust has to overcome this velocity which is almost impossible or not feasibly achievable with standard exhaust systems. Further, when utilizing very high exhaust velocities, the exhaust air flow deforms the brush bristle arrangements by bending the bristles and reducing the control capacity of the brush. When the brush does not properly cover areas of the workpiece where most emissions originated, control of the wooddust by the brush in these areas is reduced and dust is emitted into the work area. The exhaust capture capability is further reduced by blockage of work particles created at the wood surface.
While there have been a number of proposals to remove the dust produced by tool machines, these prior proposals generally, have not met with widespread acceptance. The inventors' experience is that the prior proposals do not remove an adequate percentage of the chips or waste products produced. Thus, even though a waste device may be attached to and utilized in conjunction with a machine tool, it has heretofore been the case that an excess quantity of waste is still distributed into the work area.
The present invention is an improvement over prior known dust collecting systems associated with machine tools such as routers, milling machines, drill presses and the like, which utilizes a system of jet strippers to slow the wood particles by directing an air flow at a higher velocity than the wood particles against the direction of the wood dust emission. Additionally, particles are blown out of areas blocked by the wood surface which enables the exhaust to capture these particles without any significant increase in the exhaust velocity.